I2-promoted formal [3 + 1 + 1 + 1] cyclization to construct 5-cyano-1H-pyrazolo[3,4-b]pyridine using malononitrile as a C1 synthon

A novel [3 + 1 + 1 + 1] cyclization reaction for the synthesis of compounds based on a 5-cyano-1 H -pyrazolo[3,4- b ]pyridine skeleton from aryl methyl ketones, malononitrile and 5-aminopyrazoles has been established.